1. Field of the Invention
The present invention relates generally to dry cleaning systems, and more particularly to a dry cleaning system wherein petroleum solvent vapors discharging from a dry cleaning dryer are condensed and the condensed solvent vapors are separated from a condensing liquid so the liquid solvent may be reused.
2. Prior Art
There are two distinct types of solvents used in the dry cleaning industry, namely "synthetic solvents" and "petroleum solvents." The so-called "synthetic solvents" are halogenated hydrocarbons such as perchloroethylene, 1,1,2-trichloro-1,2,2-trifluoroethane (Freon 113), trichlorethylene, carbon tetrachloride, and the like. The so-called "petroleum solvents" are petroleum distillate fractions and have been categorized by the International Fabricare Institute as being of various types including Stoddard solvents, solvents meeting "140-F" specifications, odorless solvents, low end point solvents and the like. Due to its acceptance in the industry, the term "petroleum solvent" is here intended to include petroleum distillate fractions used as dry cleaning solvents while the term "synthetic solvent" is intended to include halogenated or similarly treated hydrocarbons used as dry cleaning solvents.
The synthetic solvents are characteristically expensive and have, in the prior art, been reclaimed by condensing solvent vapors for reuse as disclosed in U.S. Pat. Nos. RE 19,986 and 3,110,544. Condensation units designed to reclaim synthetic solvents are expensive systems normally incorporating substantial lengths of cold water condensing coils. Petroleum solvents, on the other hand, are substantially less expensive and their vapors have been discarded, although the condensation and recovery thereof is suggested in U.S. Pat. No. 1,795,006. The accepted practice of discarding petroleum solvent vapors is a substantial waste of a valuable chemical resource.
In addition to the problem that venting solvent vapors to the atmosphere is wasteful, it also creates an air pollution problem. Yet, at present, the only commercially available solutions to the recovery of petroleum solvent vapors require the use of either carbon absorption units or the use of the same condensation type reclamation units that are used to recover synthetic solvent vapors. Both of these solutions are regarded by the industry as far too expensive to warrant adoption for the recovery of petroleum solvent vapors. While the air pollution problem could conceivably be resolved by burning the vapors, this solution is unproven and could create additional unforeseeable air pollution problems. Moreover, burning the vapors provides no recovery of the solvent for reuse.
Still another drawback of present day systems which discharge heated mixtures of petroleum solvent vapors and air to the atmosphere is that no recovery is made of the substantial amount of heat energy in these mixtures. Much heat energy is wasted by these systems.